"Understanding Unix/Linux Programming: A Guide to Theory and Practice" by Bruce Molay does a wonderful job of diving into the workings of the Linux kernel without any prerequisite knowledge beyond an understanding of C. This book focuses on deconstructing common commands such as "tail" and "who" and explaining almost line-by-line how they work and interact with the rest of the system.

It appears to be a bit expensive at the moment, but it's commonly used as a textbook, so there's a plentiful used market for it.

http://www.amazon.com/Understanding-UNIX-LINUX-Programming-P...